Technical Abstract:
The peanut spotting is a big problem responsible for significant loss by the peanut industry. The cause of the spotting has been identified in the lab as being due to infection by fungi. Secondary fungal metabolites and peanut stilbene phytoalexins were not involved in the spot formation. The nature of spotting has not been fully characterized, but suggested as being due to a non-enzymatic browning. Significant changes in sugars and proteins upon peanut blanching contribute to the spotting. Compounds that produced orange, green, and blue fluorescence have been isolated from spotted peanuts and analyzed by HPLC-MSn. Those are colorless low-molecular weight compounds that could be considered early indicators of browning. Isolated colored compounds had very complex composition and were similar to compounds yielded from the Maillard reaction. Preliminary data indicated that the brown color of the spots is formed in part by high-molecular weight melanoidin polymers generated by condensation of heterocyclic subunits. Structural elucidation of the pigmented components is crucial for the determination of the nature of spotting. The peanut industry will benefit from knowledge of the exact chemical cause of spotting because further specific actions may be taken to prevent the problem.